I have just added the two Apple Refurbished 2nd generation apple HomePods to AppleCare+, giving me two years of coverage on these devices. The complimentary 7 days of appleCare+ coverage expired yesterday, 16 days after their purchase and 15 days after their first use.
AppleCare+ for two HomePods plus the refurbished purchase price was still less than the new price of the two HomePods.